In Long Term Evolution (LTE), in order to achieve a further increase in a system capacity, a further increase in a data transmission rate, and further reduction of latency in a radio section, a radio communication scheme called 5G has been studied. In 5G, various element techniques have been studied in order to satisfy requirements that latency of a radio section be less than or equal to 1 ms while achieving throughput of greater than or equal to 10 Gbps.
In 5G, a higher frequency band than that of LTE is assumed to be used. Here, since a propagation loss increases in a high frequency band, the application of massive Multi Input Multi Output (MIMO) in which beam forming with a narrow beam width is performed has been studied to compensate for it. Massive MIMO is a large-scale MIMO in which a plurality of antenna elements (for example, 100 elements) are installed at a base station side, and it is possible to reduce interference between users since it is possible to concentrate an electric field strength in a narrow region.
FIG. 1A illustrates an example of beam forming performed by a base station according to a related art such as LTE, and FIG. 1B illustrates an example of beam forming performed by a base station using massive MIMO. As illustrated in FIG. 1B, it is possible to transmit radio signals far away through beam forming with a narrow beam width. In massive MIMO, high speed communication can be achieved by performing spatial multiplexing while highly controlling a plurality of beams between a base station and a mobile station. FIG. 2 illustrates an example where two beams are spatially multiplexed while performing beam forming in both a base station and a mobile station.